Conventionally, a backlight serves as a light source of a liquid crystal display (LCD) panel for continuously illuminating light. By using a pixel electrode to control the light-shielding degree of the liquid crystal molecules, the LCD panel produces darkness or brightness variations so as to achieve display target. Since the pixel electrode fails to control all of the liquid crystal molecules, the brightness of the uncontrolled regions is unchangeable and thus the contrast ratio of the LCD panel is impaired.
As known, contrast ratios are important factors that influence the performance of LCD panels. For increasing contrast ratios, a conventional method uses a light-shielding structure to shield the light scattered from the regions uncontrolled by the pixel electrode. Generally, the light-shielding structure is made of opaque metallic material (e.g. aluminum). Since a common ground wire and a gate conductor of the LCD panel are also made of such opaque metallic material, the light-shielding structure is simultaneously defined when the common ground wire and the gate conductor are formed.
FIG. 1A is a schematic top view illustrating a conventional LCD panel. FIG. 1B is a schematic cross-sectional view of the LCD panel of FIG. 1A taken along the line A-A′. As shown in FIGS. 1A and 1B, the light-shielding structure 13 is arranged on a light-transmissive substrate 10. The light-shielding structure 13 is also arranged under a dielectric layer 19 and a data line 14 so as to enhance the light-shielding efficacy at the regions along the data line. Since no conductor is connected to the light-shielding structure 13, the light-shielding structure 13 is a floating structure. As previously described, the light-shielding structure 13, the common ground wire 11 and the gate conductor 12 are simultaneously defined by an opaque metallic layer in the same photomask processing procedure. For preventing the light-shielding structure 13 from being contacted with the common ground wire 11, the gate conductor 12 or other conductors, the light-shielding structure 13 is not extended to the data line 14 and a crossover region 15 between the common ground wire 11 and the gate conductor 12. That is, the crossover region 15 corresponds to a hollow portion of the light-shielding structure 13. Since the crossover region 15 is almost not shielded by the light-shielding structure 13, a light leak problem occurs in such a crossover region 15. The light leak problem usually results in a poor contrast ratio. In addition to the crossover region 15, the light leak problem occurs in the region around a contact hole conductor (not shown).
For solving the light leak problem, a silicon nitride (SiNx) film (not shown) is formed on the data line 14 to reduce amount of light leakage. Since an additional photomask processing procedure is required to form the silicon nitride (SiNx) film, the conventional method is not cost-effective.